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><A
NAME="TEST-PARSER"
>F.42. test_parser</A
></H1
><P
>  <TT
CLASS="FILENAME"
>test_parser</TT
> is an example of a custom parser for full-text
  search.  It doesn't do anything especially useful, but can serve as
  a starting point for developing your own parser.
 </P
><P
>  <TT
CLASS="FILENAME"
>test_parser</TT
> recognizes words separated by white space,
  and returns just two token types:

</P><PRE
CLASS="PROGRAMLISTING"
>mydb=# SELECT * FROM ts_token_type('testparser');
 tokid | alias |  description
-------+-------+---------------
     3 | word  | Word
    12 | blank | Space symbols
(2 rows)</PRE
><P>

  These token numbers have been chosen to be compatible with the default
  parser's numbering.  This allows us to use its <CODE
CLASS="FUNCTION"
>headline()</CODE
>
  function, thus keeping the example simple.
 </P
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><A
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>F.42.1. Usage</A
></H2
><P
>   Installing the <TT
CLASS="LITERAL"
>test_parser</TT
> extension creates a text search
   parser <TT
CLASS="LITERAL"
>testparser</TT
>.  It has no user-configurable parameters.
  </P
><P
>   You can test the parser with, for example,

</P><PRE
CLASS="PROGRAMLISTING"
>mydb=# SELECT * FROM ts_parse('testparser', 'That''s my first own parser');
 tokid | token
-------+--------
     3 | That's
    12 |
     3 | my
    12 |
     3 | first
    12 |
     3 | own
    12 |
     3 | parser</PRE
><P>
  </P
><P
>   Real-world use requires setting up a text search configuration
   that uses the parser.  For example,

</P><PRE
CLASS="PROGRAMLISTING"
>mydb=# CREATE TEXT SEARCH CONFIGURATION testcfg ( PARSER = testparser );
CREATE TEXT SEARCH CONFIGURATION

mydb=# ALTER TEXT SEARCH CONFIGURATION testcfg
mydb-#   ADD MAPPING FOR word WITH english_stem;
ALTER TEXT SEARCH CONFIGURATION

mydb=#  SELECT to_tsvector('testcfg', 'That''s my first own parser');
          to_tsvector
-------------------------------
 'that':1 'first':3 'parser':5
(1 row)

mydb=# SELECT ts_headline('testcfg', 'Supernovae stars are the brightest phenomena in galaxies',
mydb(#                    to_tsquery('testcfg', 'star'));
                           ts_headline
-----------------------------------------------------------------
 Supernovae &lt;b&gt;stars&lt;/b&gt; are the brightest phenomena in galaxies
(1 row)</PRE
><P>
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